The present invention is directed to dye compositions. More specifically, the present invention is directed to dye compositions exhibiting waterfast characteristics and suitable for applications wherein waterfast images are desirable, such as ink jet printing. One embodiment of the present invention is directed to dye compositions of the formula ##STR3## wherein Cp and Cp' are each coupler compounds of the formula ##STR4## wherein the --COOH group and the --OH group can be in any position on either ring, provided that in the naphthalene ring system there is present least one hydrogen activated through resonance by the --OH group for an electrophilic aromatic substitution coupling reaction, n represents the number of substituents on the rings and is a number of from 0 to 8, and R represents the substituent groups on the ring, wherein each R is independently selected from the group consisting of hydroxyl groups, alkyl groups, substituted alkyl groups, aryl groups, substituted aryl groups, aryl-alkyl groups, substituted aryl-alkyl groups, halogen atoms, and nitro groups. Another embodiment of the present invention is directed to a process for making the aforementioned dye which comprises (a) reacting 4,4'-diamino-2,2'-stilbene disulfonic acid with a base, hydrochloric acid, and a nitrite salt, said reaction taking place in aqueous solution, thereby forming a diazonium intermediate; and (b) reacting the diazonium intermediate with an alkaline aqueous solution containing a coupler compound of the formula ##STR5## wherein the --COOH group and the --OH group can be in any position on either ring, provided that in the naphthalene ring system there is present least one hydrogen activated through resonance by the --OH group for an electrophilic aromatic substitution coupling reaction, n represents the number of substituents on the rings and is a number of from 0 to 8, and R represents the substituent groups on the ring. Yet another embodiment of the present invention is directed to an ink composition for ink jet printing which comprises an aqueous liquid vehicle and the aforementioned dye composition. Still another embodiment of the present invention is directed to a process for making the aforementioned ink composition which comprises (a) reacting 4,4'-diamino 2,2'-stilbene disulfonic acid with a base, hydrochloric acid, and a nitrite salt, said reaction taking place in aqueous solution, thereby forming a diazonium intermediate; and (b) forming a dye composition by reacting the diazonium intermediate with an alkaline aqueous solution containing a coupler compound of the formula ##STR6## wherein the --COOH group and the --OH group can be in any position on either ring, provided that in the naphthalene ring system there is present least one hydrogen activated through resonance by the --OH group for an electrophilic aromatic substitution coupling reaction, n represents the number of substituents on the rings and is a number of from 0 to 8, and R represents the substituent groups on the ring; and (c) admixing the dye compound with water to form an ink composition. Another embodiment of the present invention is directed to an ink jet printing process which comprises incorporating the aforementioned ink composition into an ink jet printing apparatus and causing droplets of the ink composition to be ejected in an imagewise pattern onto a substrate.
Colorant materials with waterfast characteristics are known. For example, U.S. Pat. No. 5,120,361 (Winnik et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition which comprises a solution comprising a dendrimer and a dye or dyes. The ink composition exhibits excellent waterfastness.
U.S. Pat. No. 5,098,475 (Winnik et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a solution with a dendrimer colored with a dye or dyes covalently attached thereto. As optional additives there may be included in the ink humectants and biocides. The aforementioned inks can be prepared by mixing the appropriate components such as a dendrimer, water and a reactive dye. Also disclosed is a process for the utilization of the aforementioned compositions and ink jet printing processes.
U.S. Pat. No. 4,963,189 (Hindagolla) discloses inks comprising (a) a dye corresponding to the formula ##STR7## wherein W is COOH, X is H or COOH, Y is H, COOH, or SO.sub.3 H, Z is H, COOH, or SO.sub.3 H, and R is H, CH.sub.2 COOH, or CH.sub.2 CH.sub.2 COOH; with the proviso that there are at least two COOH groups and that the number of COOH groups is equal to or greater than the number of SO.sub.3 groups, and (b) a solvent which may be water or a mixture of water and a water-soluble organic solvent. The inks preferably have a pH from about 7 to about 9.5.
Although known compositions are suitable for their intended purposes, a need remains for dye compositions with waterfast characteristics. In addition, there is a need for dye compositions which enable the production of waterfast images when incorporated into aqueous inks. Further, there is a need for waterfast dye compositions suitable for use in ink jet printing applications. Additionally, there is a need for waterfast dye compositions suitable for use in thermal ink jet printing applications. There is also a need for waterfast ink jet ink compositions. In addition, a need remains for waterfast ink jet inks of relatively simple composition, without the need for ink additives to enhance the waterfastness of the ink.